Perpendicular magnetic recording systems have been developed for use in computer hard disk drives. A typical perpendicular recording head includes a trailing write pole, a leading return or opposing pole magnetically coupled to the write pole, and an electrically conductive magnetizing coil surrounding the yoke of the write pole. The bottom of the opposing pole has a surface area greatly exceeding the surface area of the tip of the write pole.
Conventional perpendicular recording media typically include a hard magnetic recording layer and a soft magnetic underlayer which provide a flux path from the trailing write pole to the leading opposing pole of the writer. To write to the magnetic recording media, the recording head is separated from the magnetic recording media by a distance known as the flying height. The magnetic recording media is moved past the recording head so that the recording head follows the tracks of the magnetic recording media, with the magnetic recording media first passing under the opposing pole and then passing under the write pole. Current is passed through the coil to create magnetic flux within the write pole. The magnetic flux passes from the write pole tip, through the hard magnetic recording track, into the soft underlayer, and across to the opposing pole.
Perpendicular recording designs have the potential to support much higher linear densities than conventional longitudinal designs, especially when a bilayer perpendicular media with a soft magnetic underlayer is used. Magnetization transitions on the bilayer recording disk are recorded by a trailing edge of the trailing pole and reproduce the shape of the trailing pole projection on the media plane. However, due to the change in skew angle as the recording head travels in an arc across the disk and possible misalignment of the write pole, this can result in unwanted side writing when a rectangular shaped write pole is used.
A possible solution to the skew angle problem is to change the track pitch. For example, if the pole length is equal to 0.7 micron and the skew angle is 15 degrees, the head covers a radial width of 0.17 micron. If the track width is 0.1 micron, allowing 20 percent for track misregistration, the track pitch will have to be 0.2 micron vs. 0.12 micron in the case of zero skew-angle. Such an increased track pitch significantly lowers the areal density. Another possible solution is to make the length of the write pole shorter in the direction along the tracks, which would decrease the negative effect of non-zero skew angle, but at the expense of significantly decreasing the write field. This would limit the ability of the writer to write on higher coercivity media.
The present invention provides a solution to the non-zero skew angle problem which does not require either decreasing the track pitch or any substantial modification of the overall write head design.